Background Bioelectrical impedance analysis (BIA) has been intro duced as a noninvasive, rapid, easy to perform, repro ducible, and safe technique for the analysis of body composition [1]. It is based on the assumption that an electric current is conducted well by water and electro lytecontaining parts of a body but poorly by fat and bone mass. A fixed, lowvoltage, highfrequency alter nating current introduced into the human body or tissue is conducted almost completely through the fluid

* Correspondence: ali.canbay@unidue.de 1 University Clinic DuisburgEssen, Department of Gastroenterolgy and Hepatology, Hufelandstrasse 55, 45122 Essen, Germany Full list of author information is available at the end of the article

compartment of the fatfree mass [2]. BIA measures parameters such as resistance (R) and capacitance (Xc) by recording a voltage drop in applied current [3]. Capa citance causes the current to lag behind the voltage, which creates a phase shift. This shift is quantified geo metrically as the angular transformation of the ratio of capacitance to resistance, or the phase angle (PA) [4]. PA reflects the relative contribution of fluid (resistance) and cellular membranes (capacitance) of the human body. By definition, PA is positively associated with capacitance and negatively associated with resistance [4]. PA can also be interpreted as an indicator of water dis tribution between the extra and intracellular space, one of the most sensitive indicators of malnutrition [5,6].